Gas turbine engines are commonly used for propulsion elements for aircraft. Gas turbine engines include an air intake, a compressor, a combustor, a turbine, and an exhaust nozzle. During operation, air enters the engine at the air intake and is compressed by the compressor. The compressed air is mixed with fuel and ignited in the combustor, which adds energy to the system. The combustion products, e.g., hot exhaust gases, flow through the turbine which extracts energy to power the compressor. The exhaust gases leaving the turbine flow through the exhaust nozzle to provide propulsive thrust for the engine.
A jet engine is a type of gas turbine engine that derives all of its thrust from the exhaust gases exiting the exhaust nozzle. A turbofan engine is a type of gas turbine engine that derives only a portion of its thrust from the exhaust gases exiting the exhaust nozzle. Turbofan engines utilize a fan upstream of the compressor, e.g., between the air intake and the compressor. The fan is driven by the turbine and compresses the air prior to entering the compressor. A portion of the air that is compressed by the fan bypasses the compressor, combustor, and turbine. The total engine thrust is a function of both the bypass air and the exhaust gases. In high bypass ratio engines, the majority of the thrust is derived from the fan rather than the exhaust gases. In low bypass engines, more of the thrust is derived from the exhaust gases.
Many existing gas turbine engines have lower than optimal thrust. Attempts to address thrust issues include thrust vector control systems, which add complex moving parts to the exhaust section of the engine for changing the shape of the exhaust nozzle. However, thrust vector control systems add a large amount of weight to the aircraft due to the added structural elements (e.g., movable deflectors) and the actuators associated with these elements. Any increase in thrust is typically negated by the added weight, such that the overall efficiency of the engine is actually reduced. Moreover, thrust vector control systems with movable structural elements, such as movable deflectors, disadvantageously add complexity to the aircraft. Furthermore, thrust vector control systems are not appropriate for use with rockets because the thrust vector control systems do not provide sufficient control for such rockets that are put into operation according to the situation.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.